When cell phones first came out, you had to pay by the minute for calls. Then the standard became unlimited minutes.

When texts became the new form of communication, you had a limit on texts and overage charges. The standard eventually became unlimited texting.

Unlimited data was offered for a while until technology made it such that massive quantities of data could be quickly and easily consumed (ie Netflix, etc.), so cell phone service providers said "hey, we need to make as much money as we can off of this while we can!" But now data transmission is the de rigueur form of communication. Snapchat, Instagram, Facebook, etc. All data based.